The Science Behind Spilled Coffee

Science may not have discovered a cure for cancer, but they are hot on the trail for the answer to why coffee spills. A new research study by physicists Hans Mayer and Rousian Krechetnikov at the University of California, Santa Barbara delves into what some are calling the "Science of Slosh."

"Each morning, blurry-eyed physicists try to solve a frustratingly complex mechanical problem: how to walk with a full cup of coffee, without letting it slosh over the sides," says the authors of the article published in the journalPhysics Review E. According to their findings the mug may be the culprit. "The sloshing of liquid in a cylindrical container, like a mug, is similar to the motion of a pendulum," the study explains. "In a typical mug, 7cm in diameter and 10 cm tall, the lowest frequency oscillation of the coffee rocking back and forth in the cup is easily excited by walking at a normal pace." But it's not just the motion or pace at which you walk through your office halls, sound is also a contributing factor. The steps of your shoes or the noise from the movement of the cup that is indiscernible amplifies those oscillations which leads to spills.

How did they find this out? The researchers asked volunteers to set on a straight path with a full coffee mug while also looking straight ahead. The mug was rigged with a small sensor and a camera recorded the motion of the subject. What they determined was, the fluid has a natural frequency which is determined from the carrier in which the liquid is contained. It comes as no surprise that the less uniformity to a person's gait, the more likely they are to spill.